Beverage dispensers are well known in the art and are typically used to dispense carbonated beverages consisting of a combination of syrup and carbonated water. Beverage dispensers of the ice bank variety use refrigeration equipment including a compressor, condenser and evaporator to form an ice bank around the evaporator coils. The ice bank is suspended in a tank of cold water and provides a cooling reserve for the carbonated water and syrup beverage constituents.
A major problem with the ice banks concerns the regulation of the size thereof. Mechanical and electro-mechanical controls are known, however such controls can be slow to respond and therefore result in wider than desired fluctuation in the size of the ice bank. Electronic controls are known whereby a pair of probes determine the presence of ice or water as a function of the conductivity thereof. However, early electronic controls suffered from reliability problems, and the probes over time can become corroded and therefore provide unreliable information. Furthermore, both mechanical and electronic controls have the problem of hysteresis management wherein undesirable short cycling of the refrigeration compressor can occur. Such prior art controls have not been able to determine with a high degree of certainty if ice is present, and if so is there is sufficient thickness that further ice production should be terminated.
A similar problem exists in current art beverage dispensers with respect to the carbonator. The carbonator, of course, is the vessel wherein plain water and carbon dioxide are combined to produce the carbonated water. Typically, a carbonator includes a probe positioned therein having high and low probe contact points for electronically determining the level of water within the carbonator. Specifically, the probes determine the presence of water or air with respect to the difference in electrical resistance there between. Prior art level controls of this type, as with ice bank controls, suffer with the problem of accuracy. The interior of the carbonator is a dynamic environment where water and carbon dioxide are being combined causing turbulation and spray. Thus, it has always been difficult to know if the water is in fact sufficiently low to require water to be pumped to the carbonator. Since it is difficult to know the level of the water in the tank, it is also difficult to build in any form of hysteresis control so that the pump is not short cycled.
A further problem with prior art dispensers of the ice bank type concerns the control of the agitator motor. The agitator motor is used to circulate water within the water tank in which the ice bank resides to enhance heat exchange between the ice and the water and ultimately the beverage constituents. In such prior art dispensers agitator motors are generally operated continuously. However, such use of electrical power is wasteful, especially during periods of time wherein the dispenser is not in use. Thus, it would be desirable to operate the agitator motor more in accordance with the actual need thereof.
It is also known that the carbonator can become less effective at carbonating plain water over time. This can occur as a result of oxygen and other gases entrained in the water being released therefrom within in the carbonator. Eventually, the air space within the carbonator that is ideally totally carbon dioxide, can include a substantial percentage of oxygen, nitrogen, and so forth. Thus, various strategies have been proposed to use a solenoid operated valve to periodically vent air from the carbonator air space and replace it with carbon dioxide. However, such devices typically purge air from the carbonator based upon a predetermined time lapse. It would be more desirable to purge the carbonator based more directly upon the actual presence of contaminating gases as opposed to the lapse of a predetermined period of time where such purging may occur needlessly.